Thermionic device



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THERMIONIC DEVICE Original Filed Oct. 21, 1950 2 Sheets-Sheet l IN VEN TOR y 1935.. c. H. BRASEL'iON zmwm THERMIONIC DEVICE Original Filed Oct. 21, 1930 2 Sheets-Sheet 2 Hlllllllllllll "II "III! [III IIH Hl IN VEN TOR Patented July 9, 1935 action PATENT orFiC- r :THERMIONIC DEVICE Chester 11. BraseltonyNew York, N. Y., assignor poration of Delaware Ann rat on toiSiriauLjamp Company, Newark, N. 1., a coroeto'bs 21:, 1930, Serial No. 490,126, Renew d A il .93:5,

Claims. (01. 250-2715) This. invention relates to thermionic devices used: asrectifiers, amplifiers, or detectors in elec-. trical circuits. L i

One. of: the objects of: the invention is, to provideacathodefor. a thermionic'device which is simple andeasily constructed.

Another object or the invention isvhto provide a cathode for a thermionic device which may have a greater resistance so. that the cathode may be energized by higher voltages. if desired.

Another object ofythe. invention is to provide a simple method of rendering a cathode electron emitting.

Other objects of the invention and objects relating particularly to. the construction and assembly of the various p-artswill be apparentas the description of the invention proceeds;

One embodiment of the invention has been illustrated in the accompanying drawings in which: v

Fig. l is a front elevational view of a thermie onic device partl in section andwith one-half of the anode removed to'show the interior parts; Fig. 2 is asec-tional side elevational'view of the elements of the device. shown in Fig. 1;

Fig. 3 isa sectional. front view of a heatertype thermionic tubeembodying the invention; and

Fig. 4 is a sectional side view of the elements ofFig. 3;

heater element. I

Referring now more specificallyto Figs. 1 and 2 of the. drawings the invention is shown in a thermionic device comprising an envelope ll] of glass or other desirable material sealedin the usual manner to a press it which supports the various elements of the device. The elements comprise an anode l2, a grid l3, and a cathode l4. t.

The anode t2 maybe formed of two'plates each having asemiecylindrical portion l5 with a flange 16 at each sidethereof extending -radi.-v ally-therefrom. The flangeslfi may be'provided with grooves IT adjacent their outer edges to receive a pair of support rods l8 which may ex.- tend parallel to each other and may be bent inwardly and downwardly and tobe. sealed in the press I t. When the two. plates for the anode. are

. assembled upon the support rods they may be Welded to the support rods so that a cylindrical anode is formed with a flange at each side thereof attached to. one of the support rods It.

The'helieal grid is may besupported upon a supportrod H? as by weldingthereto-i and; this 5.5 rodinayibe'welded to a support rod 2B which is 0f the coil maybe conne ted to he support d Fig. 5. is an enlarged view. of oneendof the sealed in the press it while the upper end may; be welded toan angular 1'06. 28 which may extend bachwardly and be bent downwardly to be eal d in a glass head, 22?. The upper ends of, the sup: port rods it, may also be bent backwardly and- 5 downwardly and may be sealed in the bead 2'2.

v The cathode i l positioned inside of the grid l3 may comprise a core 23' of electron emitting material which may be any of the materials commonly used" for that purpose such as the oxides of the alkali earth metal group or mixtures of such oxides held together'w-ith a suitable binder.

Around the core 23?,may be wound a core 24 of;

resistance wire such as tungsten, molybdenum, tantalum, or nichrorne, and the core maybe held inside of the coil by slightly, deiorming the coil; at. each end of the core. The wire may be wound around the core or the coil may be formed; first and the coil slipped insideof it. either case the core is in Contact with the turnsof the coil A d he ps t hold t o l to pr v n t turns from touching each other. The lower endof the coil may be attached to a support rod 25 which may be sealed in the press H and the upper end 216 wh ch may xt nd arwardlv and b be downwardly parallel to the anode and inwardly a ai b eath th a od an ownward y again to the press 1 i in whic t. ma als be s aled hus the supportrcds 25; and 25 f rm the filament o ethode'l adsiort ede ce. a a h r a ular co n to El ma e sealed in h bead 22 nd ma e Welded o. t e support rod 26 o. n horthe h ad. th res ec to. the upport. r d h reby din he ppe ndsjo the other ments i id posi on head nsrih Wires. 2 29. ehdtil ma be co nec ed c. he up ort s it t nd 35 wh ch may we. be conn cted to e 3i, 3%, it, n 3. mo nte on th e 35; vsch may b 1 at ached in h usua a ne as y cementi to he n el pe l i- V If desired the envelope it! maybe exhausted to pe ateth vdevice i a ac um or it ma b d a a le to d a pu e n rt as w th a pressure n t e n i h o hood o 200 mmof Any inert a may be u ed but I P e e h sasc su h a a s n e n el um ryptch X on Q mix u the e ses or f d si ed c r ai me al v s ma be mix d ith th t or cases to increase th on uctiv t of the de ice- Th se metal vapors ma e the va rs of m re i rubidium. caesium, a ci m, or ca m um they m ybe in ro c d into; the bulh b previ insa sa t such a arvchloridc. o the dcsi tti tetal in a container 36 made of pressed metal with a small piece of magnesium. When the container 36 is heated as by external bombardment after the envelope is sealed off the magnesium will combine with the chloride of the desired metal liberating the free metal and forming magnesium chloride. The free metal will condense on the walls of the envelope to be evaporated again when the envelope is heated in use. The container 36 may be attached by means of a support wire 3'! to one of the support rods, as the rod IB, as indicated.

In Figs. 3 and 4 the invention is shown in connection with a heater type tube. In this construction a coil 38 of resistance wire similar to the coil in the other figures is provided with a core 39 of electron emitting material similar to that already described. The coil may be mounted at its lower end upon a support rod 40 which may be sealed in the press 4| and at its upper end upon a support rod 42 which may extend backwardly, down- Wardly, and inwardly again to be sealed in the press 4|. A cylindrical cathode 43 may be provided surrounding the coil 38 but spaced therefrom and the cathode may be supported at its lower end by means of a strap 44 extending around the cathode and welded to a support rod 45 sealed in the press 4|. The upper end of the cathode may be supported by means of a strap 46 which extends around the end and may be welded to a short support rod 41 sealed in a bead 48 similar to the bead described in connection with the previous figures. The cathode may be coated as indicated in Fig. 4 with electron emitting material 49. The glass bead 48 may be rigidly held in position by a short angular connector 50 which may be sealedin the bead and welded to the support rod 42.

A helical grid 5| may be provided similar to the grid already described and it may be held in position by a support rod 52 which may be welded or otherwise attached at its lower end to a short support rod 53 which is sealed in the press 4| and at its upper end to an angular support rod 54 which may be sealed in the bead 48.

An anode 55 similar to the anode described in connection with Figs. 1 and 2 may surround the grid 5| and may be supported upon two support rods 56 which are sealed in the press 4| and having their upper ends welded to two angular support rods 51 which may be sealed in the bead 48.

Leading-in wires 58, 59, 60, BI, and 62 may be connected respectively to support rods 56, 53, 40, 42, and 45 and the tube is adapted to have a five terminal base (not shown) with a separate terminal for the cathode connection.

In this device the cylindrical cathode is heated to electron emitting temperature by radiation from the coil of filament wire and also by electron bombardment from the core of emitting material. The tube may be operated in a vacuum or may be provided with a gas as described in connection with Figs. 1 and 2.

In preparing either of the constructions shown and described the following process as described in my copending application Serial No. 459,048, filed June 3, 1930, is recommended:

With the elements all mounted in the envelope as shown the envelope may be comiected to an exhaust pump and an oven placed over it in the usual manner to raise the temperature to between 350 to 400 C. A current may be run through the filament at this time to raise the temperature thereof to approximately 600 C. to drive out the occluded gases in the filament and other parts of the envelope. When no more gases appear in the envelope as is evidenced by the lack of fluorescence when high tension current is directed against the envelope from an induction coil the filament current may be increased to approximately 800 C. This drives out the binder from the electron emitting material and other occluded gases. When no more gases appear in the envelope the oven may be raised and the filament current increased for a moment to raise the temperature to less than 1200 0., the vacuum pump being connected all this time to remove the gases as they are driven off.

When the envelope is again free of gases the vacuum pump may be shut off, the current turned ofiT, and a slight amount of an inert gas, such as neon at a pressure of about mm. of mercury, may be admitted into the bulb and the filament current turned on again and gradually increased. Spots of localized discharge will then appear having a reddish color and will gradually spread until the discharge fills the entire bulb. This appears to activate the electron emitting material and should be carried on until the discharge completely fills the bulb which should take less than ten minutes. If white discharge spots appear on the filament or other parts of the device it is an indication that all of the gases or vapors have not been removed and the exhaust pump should again be connected and the tube exhausted and the whole process of activation repeated.

When the activation process is completed the filament current may be increased for a moment to raise the temperature to about 1400" C. and then the exhaust pump connected again to remove the gases. A high vacuum of about .5 micron is preferably obtained at this time after which the pump may be shut ofi, the filament current turned off, and the bulb may be sealed off either in the evacuated condition or after admitting the desired gases. I have found that about 50 mm. of neon and mm. of argon when these gases are chemically pure give good results although other gases as mentioned above and metal vapors may be used if desired.

Many modifications of the invention may be resorted to such as changing the shape and position of the electrodes and the elimination of the grid or the addition of more grids, and I do not therefore desire to limit myself to what has been shown and described except as such limitations occur in the appended claims.

What I desire to claim and secure by Letters Patent is:

1. In a thermionic device an anode, a cathode spaced from said anode, a heater for said cathode comprising a coil of filamentary resistance wire spaced from said cathode, and a core of electron emitting material within said coil.

2. In a thermionic device an anode, a cathode spaced from said anode, a heater for said cathode comprising a coil of filamentary resistance wire spaced from said cathode, a core of electron emitting material within said coil and in surface contact therewith, and an ionizable gas surrounding said anode, coil, and core.

3. In a thermionic device an anode, a tubular cathode, and a heater for said cathode comprising a coil of filamentary resistance wire and a core of electron emitting material within said coil and in surface contact therewith.

4. In a thermionic device an anode, a cathode spaced from said anode, a heater for said cathode comprising a coil of filamentary resistance wire spaced therefrom, a core of electron emitting material within said coil and in surface contact terial within said coil and in surface contact therewith, and a mixture of neonand argon gases therewith, and a mixture of neon and argon gases surrounding said anode, cathode, and heater. surrounding said anode,'cathode and heater, said 5. In a thermionic device an anode, a cathode gases having a pressure of approximately 200 mm. 5 spaced from said anode, a heater for said cathode of mercury.

comprising a coil of filamentary resistance wire CHESTER H. BRASELTON. spaced therefrom, a core of electron emitting ma- 

